Add less_than function utility module

This commit is contained in:
Lars Mueller 2022-10-01 18:11:44 +02:00
parent 39335cf76f
commit 4d6e5fdfb0
2 changed files with 54 additions and 0 deletions

@ -40,6 +40,7 @@ for _, file in pairs{
"schema", "schema",
"file", "file",
"func", "func",
"less_than",
"iterator", "iterator",
"math", "math",
"table", "table",

53
less_than.lua Normal file

@ -0,0 +1,53 @@
-- Comparator utilities for "less than" functions returning whether a < b
local less_than = {}
setfenv(1, less_than)
default = {}
function default.less_than(a, b) return a < b end; default.lt = default.less_than
function default.less_or_equal(a, b) return a <= b end; default.leq = default.less_or_equal
function default.greater_than(a, b) return a > b end; default.gt = default.greater_than
function default.greater_or_equal(a, b) return a >= b end; default.geq = default.greater_or_equal
function less_or_equal(less_than)
return function(a, b) return not less_than(b, a) end
end
leq = less_or_equal
function greater_or_equal(less_than)
return function(a, b) return not less_than(a, b) end
end
geq = greater_or_equal
function greater_than(less_than)
return function(a, b) return less_than(b, a) end
end
gt = greater_than
function equal(less_than)
return function(a, b)
return not (less_than(a, b) or less_than(b, a))
end
end
function relation(less_than)
return function(a, b)
if less_than(a, b) then return "<"
elseif less_than(b, a) then return ">"
else return "=" end
end
end
function by_func(func)
return function(a, b)
return func(a) < func(b)
end
end
function by_field(key)
return function(a, b)
return a[key] < b[key]
end
end
return less_than